1. Technical Field of the Invention
This invention relates to system management of data. More particularly, it relates to system control of compression and decompression of data based upon system aging parameters and demand such that compressed data becomes a system managed resource.
2. Background Art
In the interactive commercial business environment, data sets are often very large. One example of this is databases, which may be spread over several storage devices, such as direct access storage devices (DASD), on several DASD controllers and increasingly over several interconnected machines.
More efficient use may be made of storage attached to a computer if data can be compressed before it is stored. Multi-fold compression ratios can be achieved with algorithms currently available for some data set contents. Often, frequent access is limited to some subsets of these data sets, and further to certain subsets of the data set itself. Data sets of the size common on commercial business machines render full file based data compression such as `terse` unacceptable for anything other than long-term archives. Furthermore occasional usage requires the entire dataset be decompressed at first access. The commercial business environment is highly interactive. To be of value, data must be made available on demand without manual intervention.
Also, in the IBM AS/400 System, compression is offered with all functions provided by software. Such software compression allows for the compression of objects with performance in the 70-80 thousand (K) byte range. There is a need in the art for hardware compression to enhance and extend compression to database, office, and spool files.
It is an object of the invention to provide a practical method to segment large files and perform efficient compression. It is a further object of the invention to apply compression more efficiently to large databases, portions of which may be used more frequently than others.
It is a further object of the invention to provide a system and method for managing data, with compressed data managed as a system resource based upon aging and demand.